OBD II Codes - P0224 & P0455 on 2001 Dodge Ram 1500

Problem:
Tried to get the truck inspected, but got these two errors. First time only the P0455. Second time both P0455 and P0224. Just bought the truck, don't know anything about it.
Actions:
Replaced gas cap already.
Question:
How do I find the problem and how do I fix it.